Much has changed since ADOT got its start in 1927.
Back then, the agency was known as the Arizona State Highway Department and roads certainly were built a little differently. Methods, materials and technology have changed so much since then.

If you drive Valley freeways during rush hour, you’re probably pretty familiar with ramp meters …
They’re the two-light signals positioned at most Valley on-ramps that tell motorists when it’s okay to head onto the freeway.
Ramp meters have been used in the Phoenix-Metro area for about the past 20 years and maybe you think not much about them has changed … but, actually they’ve recently become much more efficient!